Tuesday, 20 December 2016

Gem Butterflies

The incredible colours of rhodochrosite, haüyne, sphene, yogo sapphires, tanzanites, hiddenite, garnets and benitoites at the Los Angeles County Natural History Museum, in the Butterfly Broach Collection.

This brooch is almost entirely set with benitoite, the California state gemstone.

A barium-titanium silicate mineral (BaTiSi3O9), benitoite is a rare mineral, crystals large enough to be cut into gemstones are found only in one location: the Dallas gem mine in San Benito County, California. An unusual geologic setting of hydrothermal veins between glaucophane schist and serpentinite created this rare mineral. Benitoite is known for its high dispersion and its vivid blue fluorescence in UV light.

Orange spessartine garnets from the Little Three mine in Ramona, California highlight this brooch, along with colorless diamonds and green tsavorite garnets from Kenya.

The multi-colored sparkle of this butterfly emanates from its green titanites (“sphene”) from Madagascar.
The "fire" of titanite derives from its high dispersion and refraction. Titanite (CaTiSiO5) is a fairly common accessory mineral in igneous and metamorphic rocks,
but is seldom found in size and quality suitable for gems.

This butterfly brooch brings together titanites in three different colors: green from Madagascar, brown and yellow from Pakistan.

A 13.51ct rhodocrosite (MnCO3). This mineral is very rare in jewelry. Apatite and opal cover the wings, the eyes are green chromium-rich titanite (sphene).

Pink and red spinels from Vietnam highlight this butterfly brooch. Red spinel (MgAl2O4) has long been used as an affordable alternative to ruby. Some famous historical rubies are actually red spinels. Spinel is now very popular in its own right. The eyes of the butterfly are blue jeremejevites (Al6(BO3)5(F,OH)3) from Namibia.

A 10.01-ct green hiddenite is the central piece of the brooch. Hiddenite is a green variety of the mineral spodumene (LiAl(SiO3)2) in which the color is caused by small amounts of the element. chromium. Hiddenite from North Carolina is found associated with emerald, the green variety of beryl, which also owes its color to chromium. The body of this butterfly is the world's largest faceted hiddenite.

This butterfly brooch is set with blue sapphires from Yogo Gulch, Montana. Sapphire senso stricto is the blue variety of corundum (Al2O3).